Smallpox is a very serious disease; it is contagious and sometimes fatal. Smallpox is caused by a germ called variola virus.

The symptoms of smallpox begin with high fever, head and body aches, and sometimes vomiting. These symptoms are followed by a rash that spreads from the head and extremities toward the center of the body, then progresses to raised bumps that eventually scab over and fall off after about three weeks, leaving a pitted scar.

Smallpox can cause:

A severe rash covering the whole body that can leave permanent scars.

High fever.

Severe headache or body ache.

Death (in about 30% of infected people).

Blindness in some survivors.

Natural cases of smallpox have been eradicated. The last natural case of smallpox was in Somalia in 1977.

The incubation period for smallpox is about 12 to 14 days (range: 7 to 17 days) after exposure.

Is smallpox fatal?Most patients infected with smallpox recover. Smallpox kills about 3 out of 10 people infected. Many smallpox survivors have permanent scars over large areas of their body, especially their face. People who survive smallpox have lifelong immunity against smallpox.

Is smallpox contagious? How does smallpox spread?

The disease usually requires face-to-face contact with a contagious person for several hours. Contact with infected skin could also transmit the virus. Spread by contact with inanimate objects (e.g., clothing, towels, linens) would be less common.

People with smallpox are contagious from when their temperature goes over 101°F (38.3°C). They stay contagious until all their scabs fall off.

Not everybody who talks with a smallpox patient will get the disease. People with smallpox can infect about half of the people who live in their household. On average, each infected person can infect about 5 other people. Those other people show symptoms about 15 days after exposure.

The most common way to transmit smallpox would be from prolonged face-to-face contact. People infected with smallpox exhale little droplets that carry the virus to the nose or mouth of bystanders. The greatest risk comes from prolonged face-to-face contact (6 feet or less, most often after 1 or more hours), with an infected person, especially one who is coughing. Indirect contact through fine-particle aerosolization or contaminated inanimate objects can spread the virus as well, though less efficiently.

Special precautions need to be taken to thoroughly clean all bedding and clothing of smallpox patients with bleach and hot water. Disinfectants such as household bleach or hospital-approved quaternary ammonia disinfectants can be used for cleaning contaminated surfaces.

Animals and insects do not carry or transmit smallpox disease. Smallpox is not spread by food or water.

Is there any treatment for smallpox?Smallpox can be prevented through the use of the smallpox vaccine. There is no proven treatment for smallpox, but research to evaluate new antiviral agents is ongoing. Preliminary results with the drug cidofovir suggest it may be useful. The use of cidofovir to treat smallpox or smallpox vaccine reactions requires the use of an Investigational New Drug (IND) protocol and should be evaluated and monitored by medical experts. Patients with smallpox can benefit from supportive therapy such as intravenous fluids, medicine to control fever or pain and antibiotics for any secondary bacterial infections that may occur.

How many people would have to get smallpox before it is considered an outbreak?One confirmed case of smallpox is considered a public health emergency.